TORONTO — When you are young, birthdays are milestones. They represent all the new and exciting things that are now at your disposal. You can get your driver’s license at 16, vote when you are 18 and walk into a bar and order a beer when you are 19. As you get older, the reverse starts to occur. Birthdays become a reminder of what you can no longer do.

Roger Federer turned 33 on Friday and while he celebrated the occasion with cupcakes following a tense, three-set match against Marin Cilic late on Thursday night, the actual birthday was yet another signpost on the journey to the end of his career.

Sure, Federer is still the No. 3 player in the world and is playing the same graceful, seemingly effortless style that has allowed him become one of the greatest players of all time. He is still the favourite to win the Rogers Cup and a lot of other tournaments he enters, but he is at a stage in his career where he is now looking back rather than forward.

Roger Federer of Switzerland celebrates his win against Marin Cilic of Croatia during Rogers Cup at Rexall Centre at York University on August 7, 2014 in Toronto, Canada. (Ronald Martinez/Getty Images)

When asked what has been his biggest achievement — a question Federer has only started hearing in the last few years — he joked, “Becoming 33 has been my biggest one.”

“I don’t know,” he said when pressed for an answer. “I mean, for me maybe becoming world No. 1, you know, or winning Wimbledon probably, something like that. Just making it on the tour overall. It was not like a goal for me. It was more like a dream, you know. So, anyway, so much more than I ever thought it would be. I always say that. I know it’s a boring answer but it really is the case.

“I just want you people to understand that, that one tournament more or less at this point doesn’t change much, but it’s in the emotions and in the grind or in the enjoyment or in the way that I play that I really can actually enjoy it out there.

“So for me probably becoming world No. 1 in 2004 or winning Wimbledon 2003 was one of my biggest moments.”

Will there be any more big moments for Federer? We’re sure hoping so, because as his coach and former world No. 1 Stefan Edberg recently said, “If Roger is still in the game, it’s great for tennis.”

Federer might still be in the game, but it’s not quite the same as it used to be. The last time he held the No. 1 ranking was two years ago. He has gone the same amount of time without winning a Grand Slam. The father of two sets of identical twins is third in the pecking order behind Novak Djokovic and Rafael Nadal, perhaps on par or maybe even behind Andy Murray and Stan Wawrinka.

Roger Federer last won a Grand Slam two years ago. (Ronald Martinez/Getty Images)

There was a point during Federer’s match on Thursday where he had seven match points in one game. He dumped a backhand volley into the net, hit another shot long and ended up losing the set in a tiebreaker.

While he eventually won, his game is no longer untouchable. He is losing more close matches than ever before. His footwork is more laboured than fluid. That trusty one-handed backhand is not quite as precise or definitive a shot as it once was. The aura of invincibility, which made it seem like he was operating with a cheat code, is fading.

Federer, who dropped to eighth in the rankings earlier this year, has lost his last five matches to Nadal and five of his last seven matches to Djokovic. In the last two years, he has won just three titles. But the most telling stat is his Grand Slam results.

The four majors, which feature best-of-five matches and twice as many players and rounds, are mental and physical marathons. They are the clearest indicator of who is the best on each surface. And they are harder to win with age.

Bjorn Borg won his last Grand Slam when he was 24. John McEnroe was 25. Pete Sampras was 31.

Federer’s last Grand Slam title came at Wimbledon in 2012, one month shy of his 31st birthday. Since then, he has made one final, two semifinals, two quarter-finals and three times failed to advance past the fourth round.

Moments after Djokovic defeated Federer in last month’s Wimbledon final, a match that lasted almost four hours and required five sets to complete, Djokovic looked at Federer and said,

“I respect your career and everything you have done. Thank you for letting me win today.”

It was a classy thing to say. And long ago, when Federer was on a ridiculous roll that saw him win 16 Grand Slams in an eight-year span, it might have seemed perfectly reasonable. But these days, Federer is no longer the best in the world. There were times this year and last where he wasn’t even the best in his own country.

And yet, we cannot write off Federer because of performances like the one in Monte Carlo in April, when he beat Djokovic in straight sets, or in the lead-up to the final in Wimbledon, when he breezed past Wawrinka and Milos Raonic without really breaking a sweat.

Last year, he said goodbye to his tiny, old-school racquet and finally switched to one that offers a much larger sweet spot in hopes of adding more punch to his shots. In January, he hired Edberg to try and coach him over the mental hurdles in hopes of grabbing one more Grand Slam title.

“What is great is he still has the determination to go out there and work hard and still has the motivation, which I think is something that’s really, really important as he sort of gets towards the end of this stage,” said Edberg. “There is still room for improvements.”

Maybe, Federer has one more in him. Maybe he will win the U.S. Open later this month and another and another.